The user can undo/redo certain commands in the VKRC viewer.
Those commands that have some additional (not visible to the user) custom data cannot be undone/redone due to Qt framework restrictions.

Every time the user inserts or modifies the text of a single block with custom data the 'undo stack' is cleaned.
Also if the user pastes, cuts or deletes a selection with more lines, of which at least one contains custom data, the 'undo stack' is cleaned as well.

Editing the following commands with custom data will cause the 'undo stack' to be cleaned:

• Motion point
• Tech command
• SERVOZANGE command
• Schritt fold in makrostep file
• Trigger fold in makrotrigger file