Making High Level Assembler code changes
In addition to COBOL and PL/I, IBM Z® Open Editor supports IBM Z High Level Assembler (HLASM) editing. You can use the following features to program in HLASM effectively.
With the syntax highlighting capability, you can quickly distinguish between labels, operations, operands, and comments in a HLASM program. With vertical rulers, which mark different areas, you can better determine correct areas for symbols, operations, operands, continuation line indicators, and sequence numbers.
The editor provides the following features and capabilities:
Browsing code by using the Outline view
As you view the source, you can use the Outline view to efficiently explore and navigate the code of the program. By looking through the items in this view, you can get an idea of what the program does at a high level and easily navigate to relevant CSECT, DSECT, MACRO instructions as well as branch labels. We purposely chose to not include every symbol because, in large assembler programs, the outline view would often become extremely cluttered. See here for instruction for how to customize what is shown in the Outline as well.

How to use it
You can use the Outline view only after you have opened a file or program. If the Outline view is not already expanded, you can open it by clicking View > Open view > Outline.
You can use this view to:
Recognize CSECT, DSECT, and MACRO instructions quickly via the icons in the outline view.
Go to a wanted location in the code by clicking that section header in the view.
Sort by Position, Name, or Type.
Search for identifiers within the outline by pressing Ctrl+Shift+O (Windows), or Cmd+Shift+O (Mac) within the Editor window.
When you move your cursor over the program, outline nodes are automatically selected. To toggle this and other features related to the Outline View, hover over the upper right corner of the Outline View. You can see the option ..., where you can click to find multiple options to organize your outline view such as Follow on Cursor, Filter by Type and Sort by Name, Position, and Type.
Code completion
When you are typing code, code completion suggestion provides you with a matching list from which you can select operations and labels. Currently, code completion for symbols only works within a single file. Work is in progress to extend this feature to multiple files.

How to use it
The code completion suggestion is displayed automatically while you are typing in an appropriate context.
Hovering for declaration
You can see hovers for operations and operands by moving your mouse curosr over the operation or operand.

How to use it
Operation and operand hovers are enabled by default. Simply move your mouse over an operation or operand. If the operand or operation is defined, a hover will appear.
Previewing copybooks
To preview the contents of a COPY statement move your mouse cursor over the copybook name. If the copybook cannot be resolved, a yellow warning underline will appear on the copybook name. To resolve copybooks, you must set special settings. Specifically, the
zopeneditor.propertygroups section of you settings.json file must be set. Please see the section below to learn how to set this setting.

How to use it
You must specify the filepath to the copybooks or include files in your settings to resolve the references. If no filepath is specified or the copybooks or include files are not found in the provided filepath, an error (red squiggle) is shown.
To resolve this, add the filepath to the references in the zopeneditor.propertygroups section of your settings.json settings as follows.
Open your settings:
Windows: File > Preferences > Settings
Mac: Code > Preferences > Settings
In the left side of the opened Settings interface, expand Extensions from the list of categories, and click IBM Z Open Editor. In the IBM Z Open Editor settings, under Propertygroups, click Edit in settings.json to open the
settings.jsonfile.Edit the
settings.jsonfile to specify filepaths to folders that contain copybooks or include files in thesyslibfield. You can hover over the field names (such asname,type) to view details about what kind of information is expected for each field.You can refer to the examples and supported patterns in Setting property groups.
Save the
settings.jsonfile by selecting File > Save.
If you have installed Zowe CLI, you can define a search path to resolve copybooks over the network against your remote MVS data sets or even USS directories (COBOL only at the moment).
To open the file in a separate editor, press Ctrl+Click (Windows) or Cmd+Click (Mac).
Operations on symbols
When you double-click a symbol to highlight the entire name and then right-click it, you can see the available operations.
How to use it
Click Change All Occurrences: Ctrl+F2 (Windows) or Cmd+F2 (Mac)
When you type the new name, all occurrences are changed simultaneously.
NOTE: In the scroll bar on the right side of the editor, each occurrence is noted with a location bar.
Click Find All References: Alt+Shift+F12 (Windows) or Option+Shift+F12(Mac)
A Results References view for the variable or paragraph is displayed on the left side of the screen. Click any result to go to that location in the file.
Click Peek References: Shift+F12 (Windows and Mac)
This opens a Results References view in the CodeLens box underneath the variable or paragraph. Click any result to go to that location in the file.

Click Go to Definition: F12 (Windows and Mac)
Go to the location where the variable or paragraph is defined. It opens the copybook or include file if applicable.
Click Go to Symbol: Ctrl+Shift+O (Windows) or Cmd+Shift+O (Mac)
When you enter an object name in the search bar or you scroll through the items to select the object, the cursor is moved to that location.
Click Peek Definition: Alt+F12 (Windows) or Option+F12 (Mac)
This opens a CodeLens box that shows where the variable or paragraph was defined in the code. If you use the keyboard shortcut Alt+F12 (Windows) or Option+F12 (Mac), the variable or paragraph name is only clicked once before the keyboard shortcuts are pressed. Double-click any result to go to that location in the file.

Syntax checking
The syntax checking feature underlines unrecognized statements and expressions in red, which helps you to make quick corrections and reduce compile errors. Currently, there are syntax errors for improper spaces in a continuation line and unresolved copy statements.
How to use it
To see all the syntax errors in the open files, open the Problems view through the View menu or by clicking the error and warning icon at the bottom in the status bar. Double-click the list item to directly go to the problem.
Undoing and redoing
Undo your changes by pressing Ctrl+Z (Windows) or Cmd+Z (Mac). Redo your changes by pressing Ctrl+Shift+Z (Windows) or Cmd+Shift+Z (Mac).