In FF[4], the latest version of the SGF standard (since 2006?), it seems to be explicitly documented how to continue beyond size 26 (sgf does not skip the "i"), all the way up to board size 52:
https://www.red-bean.com/sgf/go.html#types

So perhaps the inconsistencies you saw were either from other programs not conforming to the standard, or from choosing to implement a pre-FF[4] version of the standard? I do think there are quite a few SGF parsers that don't quite conform to the standard though which is maybe what you noticed... Go software in the wild is a bit of a mess sometimes. It's hard to get all the corners exactly right, good chance my code in KataGo doesn't either.

please add "engine match" to the "computer game" tab (autosave - games in sgf), for example like this:

the game between the two engines works great, thanks! I'm about a series of two engine games or a computer tournament. for example, two engines play 50 games and the results are saved in sgf. that is, you can leave the computer at night, and then see the games

a field that already exists, for playing variants for one game, I tried. a new game does not start, but a new continuation is played out with a certain move. it is different. Or can I somehow start the match?

number of games: 5

I want to set the move parameters for KataGo in "default_gtp.cfg", for example 500 visits. but regardless of "time" is on or off, q5go sets the move time. how to disable it? (the same in Sabaki works)
and evaluation graph works with engines? with Leela and KataGo shows nothing (straight line)

I've uploaded a 1.1.1 version which ought to fix that, as well as the board size issues that 1.1 had. There are also a handful of new features, like being able to choose a path for autosaves, and a dialog to remove old analysis from a file.

I have edited the KataGo config to 1601 visits. For example:
# If provided, limit maximum number of root visits per search to this much. (With tree reuse, visits do count earlier search)
maxVisits = 1601
# If provided, limit maximum number of new playouts per search to this much. (With tree reuse, playouts do not count earlier search)
maxPlayouts = 1601

But it seems q5go 1.1.1 ignores this setting during Batch computer analysis .
Which steps do I have to take to disable Number seconds per move during analysis?

computet vs. computer play: approximately 3 minutes after the start of the game, “engine play has completed” appears. but in "gtp.log" the engine makes a move, the game is not over! I tried different networks, 20, 10 blocks, different visits - 500, 50, boards - 29x29, 19x19. The result is the same. ("time" off, KataGo - 2 different networks. in Sabaki works)