When I want to list the permissions of a user/group, I'm only getting the permissions they're inheriting directly, but not via inheritance of other groups.
E.g.

/lp user <user> permission info // Will list the permissions the user is directly inheriting

If I do:

/lp user <user> parent add <parent>
/lp user <user> permission info // Will still list the permissions the user is directly inheriting,
but not the ones that are inherited from the group

That is how the command is suppose to work. If you're wanting to check if a user/group is inheriting a certain permission you can use the command: https://github.com/lucko/LuckPerms/wiki/Command-Usage:-Permission#lp-usergroup-usergroup-permission-checkinherits-node-context

I don't want to check the "if", but the "what"
Listing the permissions of each and every group individually to know what permissions are being inherited in total is a very tedious work

Are the developers working to fix this?

Not currently no. You have to wait until you get a rely from Luck about it.

Listing the permissions of each and every group individually to know what permissions are being inherited in total is a very tedious work

Use /lp tree

https://github.com/lucko/LuckPerms/wiki/Command-Usage:-General#lp-tree-scope-player

e.g. /lp tree . lucko

I believe that the average user will mostly want to see the permissions that are inherited directly and the ones inherited from a group

For example:

Bob
  Directly inheriting:
    permission-a
  Indirectly:
    group-a
      Permissions:
        permission-b
      Inheriting from:
        group-b: permission-c , permission-d

If there's an issue of high CPU usage on the server-side, it's also possible to use the webpage-based tree structure, like the one that the tree command generates