Most likely, this error is due to dynamicaly changed options list.
If you want to change the values of the options list, You must add:
'#validated' => TRUE
Tutorials - Drupal
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Add JavaScript as libraries
Like a CSS, You can add a JS as a librarie
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Example with a module 'mymodule'
Step 1.
Create if not exist yet, mymodule.permissions.yml (root of mymodule)
Add your new permission like:
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