Hello,
the profile is there, it is just not shown as a list. Tools > Output profiles opens the same window as the Save as dialog. At the bottom left is the selection Profiles:. Open it: below the built-in profiles and a separator line (--------------) you will find your own profiles.
When you select one of your own profiles, the buttons Save and Remove appear next to New:
- To edit it: select the profile, change the settings and click Save next to the selection.
- To delete it: select the profile and click Remove.
The page Output profiles in the PDF24 Settings only contains the Selection mode, i.e. how the profiles are shown in the window Select an output profile. The profiles themselves are not listed there.