ComicBase 2020 introduced a new feature: Grading Sets to let you tailor the list of conditions shown in each item’s drop-down. This lets you easily access any of the grades used by professional grading services like CGC, PGX, and CBCS — and at the same time, keep the conditions list trimmed down to a manageable size by eliminating any services you don’t use.
To use Grading Sets, go to the Setup > Grading, and click the Grading Sets icon at the top right:

Then, just check to enable any services you want to include in each collectibles’ conditions drop down, or uncheck unneeded ones to remove them from the list.

Note: unchecking only removes grades that are not used by items in your database.
At this time, CGC, PGX, and CBCS regular and restored grades are supported with predefined grading sets.