Installed Custom Dimensions and in the GUI I now have 5 Visit Dimensions and 0 Action Dimensions.
I added 5 action custom dimensions but gained 0, see code below. This is in accordens with the information found here https://matomo.org/faq/how-to/faq_21121/
[root@matomoprd1 matomo]# /bin/scl enable rh-php72 – php ./console customdimensions:add-custom-dimension --scope=action --count=5
Adding 5 Custom Dimension(s) in scope action.
This causes schema changes in the database and may take a very long time.
Are you sure you want to perform this action? (y/N)y
Starting to add Custom Dimension(s)
Your Piwik is now configured for up to 0 Custom Dimensions in scope action.
In the GUI I still have 5 visit dimensions and 0 action dimensions.