26668: Re-enable Add System Markings after deleting one

[krasko78]

Resolves: #26668

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[avvvvve]

tested and approved, thanks!