Wratten gels in card holders, within a plastic case large and narrow enough, with only two or three compartments, sized to fit in a front or back zippered camera bag pocket, can keep down the number of glass filters in holders, which otherwise burden the photographer.
The gel frame holder for the lens is usually narrow affaire, and Cokin plastic lens fixtures, for each lens size you carry, can hold the gels in their paper frame holders.
Even if you only carry gel filters that you only use occasionally, for getting once in a lifetime shots, together with your basic glass or plastic filters, you're just that much more prepared for whatever scene presents itself to you.
IMO.
Your filter holder is neat. But I wonder if they collect a lot of dust between uses? I keep mine in separate closeable plastic holders that they came in.