Quickadd append into properties

turns out btw, the tag picker can be used with the modal form/forms plugin

add multiselect and dataview, tick unknown values
name the property tags

in the dataview query box, enter:

[...new Set(dv.pages("").flatMap(p => p.file.tags || []))]

you can sort tags alphabetically:
[...new Set(dv.pages("").flatMap(p => p.file.tags || []))].sort((a, b) => a.localeCompare(b))

sort by frequency (slower):
[...new Set(dv.pages("").flatMap(p => p.file.tags || []))].map(tag => [tag, dv.pages("").flatMap(p => p.file.tags || []).filter(t => t === tag).length]).sort((a, b) => b[1] - a[1]).map(t => t[0])

if you add the second tag, the drop-down menu may not appear (bug?), but keep writing: the tags will appear as if by fuzzy search

you can add your new tags not in the cache as well (if you tick unknown values)

unfortunately, there doesn’t seem to be a way to add default values in the graphical user interface but you can do it in the templater code:

const result = await modalForm.openForm('add_your_form_file', {
      values: { ...frontmatter, tags: ["somedefaultvalue"] },