It certainly can be built but the volume of images one actually visits on boorus is just so enormous that perhaps only some recent 5-10k can ever be reliably tracked.

I am in the process of planning to build such function for my scripts for adult video sites, because I know that rare few will open thousands of videos per month. My script libraries can be used for booru sites but I think it would be better that you use the Grabber application from Jack Vasti which maintains many such features for boorus. I personally use it for my booru cravings.

Videos lazy loaded are currently not being handled correctly by observer function. Will be fixed in a few days.

A workaround is to click the 'Apply' button on the settings UI to apply the filters again, the usual way.

Name substitutions are not currently applied on video pages. Will add this function soon.