That sounds ok to me, although what happens if a group doesn't have such tag? Should it be considered a parent by default? In that case we don't need that tag for parents.
Now what if someone does a ...
Yes, the root groups remain the same without the "parent" tag, it should only exist in the sub-groups, it may be interesting to use a "depth" tag to know the level of the group in the structure:
Root Group (depth = 1)
"tags": [
["d", "tech"],
["name", "Tech"],
["depth", "1"],
]
Subgroup (depth = 2)
"tags": [
["d", "nostr"],
["name", "Nostr"],
["parent", "tech"],
["depth", "2"],
]
Sub-subgroup (depth = 3)
"tags": [
["d", "nip29"],
["name", "NIP-29"],
["parent", "nostr"],
["depth", "3"],
]
Root Group (depth = 1)
"tags": [
["d", "tech"],
["name", "Tech"],
["depth", "1"],
]
Subgroup (depth = 2)
"tags": [
["d", "nostr"],
["name", "Nostr"],
["parent", "tech"],
["depth", "2"],
]
Sub-subgroup (depth = 3)
"tags": [
["d", "nip29"],
["name", "NIP-29"],
["parent", "nostr"],
["depth", "3"],
]
1