To add correct idention for multi-level mail folders to correspond the level

[ratermir]

Steps to reproduce

1. create 3th (and more) level of mail folder
2. the indentation for 3th level is the same as for 2nd level (is is seen on the screen)

Expected behavior

Since the (sub)folders are tree structure, I'd epect that the indentation should correspond (at least a little) to the subfolder level, or the level should be hilited by different way (lines?). Concrete way how to achieve it does not matter, but the folder level should be sufficiently highlited and destincted.

Actual behavior

described at the beginning

Mail app version

4.1.1

Nextcloud version

18.0.2

Mailserver or service

not important

Operating system

not important

PHP engine version

None

Nextcloud memory caching

No response

Web server

None

Database

None

Additional info

No response