Sigh.......If you really want to you can use system config tool to surpass the limit or you can use multiple hdds.
But with multiple HDDs, the games will be unsorted whenever you plug in a new device.
Another way would be to:
1. have only one user on wiiu
2. set this up to have EXACTLY 300 titles. check this by deleting an entry one by one until nag disappears
3. make a second user
4. using ftpiiuanywhere, copy the barista from user 1 to user 2
5. check if all is fine by rebooting and checking both user 1 and 2 are identical and work ok
6. now you’re free to add more titles to your wiiu hard drive, noting the title ids, and OVERWRITE entries from the user 2 barista to point to the new title ids.
Use the layout from this post for this:
https://gbatemp.net/threads/wii-u-menu-info-sort-wip.454127/
Tip 1: To start, just install one more title and do this for one entry and check all is still good with the new title showing.
then repeat ad nauseam for up to 10 users and 3000 titles
Tip 2: Don’t use folders until everything is installed - makes it a lot easier to edit the files. You can folder up once your cool with your setup at the end.
Overall, I don't find your motives really logical........if it's just about preserving games, you can also store backups on a external hard drive and if you need them then you just copy it to sd and install them on the WiiU.
As already mentioned several times by others, the topic has been discussed far too often and in the end you will not find any other solution to your oh-so-horrible problem............
Btw I got this info from this thread:
https://gbatemp.net/threads/what-is-the-easiest-way-to-surpass-the-300-title-limit-in-2020.569027/