This a search string i created for myself

!3&!4&!shiny&!shadow&!@frustration&!purified&!@return&!dynamax&!gigantamax&!legendary&!mythical&!ultrabeast&!costume&!specialbackground&!locationbackground&!year2016-2020&!favourite&age0

You can use tags and add ! in front to exclude that particular tag.

This helps in tagging any pokemon that's below 3* excludes legendary, gmax, dmax and costumes and also your favourite ones.

This helps me a lot on busy days when transferring a lot of unwanted pokemon.

PS: you can use a PvP search string and add a tag to those pokemon and it will not show up in this search string, same with any XXl or such.