At present holding_strapon doesn't have a wiki definition, is applied to only a few images, and is used in a manner analogous to holding_penis as well as a character holding it loose in their hand. I'm in favor of defining it as holding a worn strapon as if it were a penis.

Perhaps an additional "holding loose/unworn strapon" or just leave it at holding_sex_toy? I could see somebody looking for something like: post #2611566

"presenting_strapon" analogous to presenting_penis?
"strapon_masturbation" masturbating with a strapon, examples: post #3051834, post #1283818 (maybe something like "futile_masturbation" for the chastity?)