The numbers of fields are in a sequence with multiples of 10. The reason for this is to allow the users to add custom fields in between if needed with numbers non multiple of 10.
The tab editor destroy that because it renumbers the whole window to multiples of 10. That can be considered a bug. It can be changed to not destroy sequences dependent of the entity type.
Or, we talked also about the tab editor to renumber the sequences as this:
Dictionary fields are numbered in multiples of 10 (like 10, 20, 30, 40 ...)
Non-dictionary fields are numbered as intermediate numbers (like 11,12,13,21,22....) - still can be possible to conflict if you have 10 intermediate fields, in such case I would think it must jump from 19 to 21 and the next dictionary would be 30.
Triaged as a potential idea due to a lack of interest from the community in 5 years.
If anyone wants to work on this, please feel free to reopen the ticket and add extra details.