partial extracted file not deleted

[ghisler(Author)]

Sorry, I thought that you were talking about PK_CAPS_BY_CONTENT, which would be 64, not 256.
If you look at the binary form of 735, 0010 1101 1111 you can see that 256 isn't part of it.
Looking from right to left, the following values are set
1 PK_CAPS_NEW: Can create new archives
2 PK_CAPS_MODIFY: Can modify existing archives
4 PK_CAPS_MULTIPLE: Archive can contain multiple files
8 PK_CAPS_DELETE: Can delete files
16 PK_CAPS_OPTIONS: Has options dialog
64 PK_CAPS_BY_CONTENT: Detect archive type by content
128 PK_CAPS_SEARCHTEXT: Allow searching for text in archives created with this plugin
512 PK_CAPS_ENCRYPT: Plugin supports encryption.

Subtracting 256 would change the flags to 0001 1101 1111, which would disable encryption and add this:
256 PK_CAPS_HIDE: Don't show packer icon, don't open with Enter but with Ctrl+PgDn

PK_CAPS_HIDE hide is meant for extensions like .docx or .chm which should still be opened with their associated program when you press Enter.

[Fla$her]

2ghisler(Author)
You're avoiding the question again. I already see descriptions of flags in the help. 735 was indicated by me after subtracting 256 from 991, I would definitely not offer to subtract it again.

I repeat: I am NOT asking about opening and viewing the archive list, but specifically about UNPACKING AFTER opening, i.e. after pressing Enter and selecting the necessary files in the archive. After that, what will the unpacking be done with — an internal function or at the expense of the plugin?

[ghisler(Author)]

PK_CAPS_HIDE has no influence on unpacking after opening. You can see what is used by pressing Alt+Enter on any file in the archive.
The internal one will be shown as 7zip (dll).
The external will be shown as the extension with which the plugin is installed.
On my system, 7z is used for the 7zip plugin and 7z2 for the Total7zip plugin.

[Fla$her]

Thanks for the reply. And why don't you add a new flag that will be responsible for unpacking? Isn't it better/faster to unpack using a built-in function, and to package using a plugin?

[nice]

for zip and rar, there's no "dll" or "not dll".
it's always "zip" and "rar" for internal and external.

[ghisler(Author)]

To force open a 7z file with a specific unpacker, you can use internal associations (open or extra verbs).
The commands would be:
**7z -> opens with the plugin defined for 7z
**internal_7z -> opens with the internal 7zip unpacker.

[Fla$her]

To force open a 7z file

Again you write about the opening. Without the 256 flag, I already get a forced opening by default. Why do I need internal associations? I suggest a flag specifically for unpacking bypassing the plugin.

[ghisler(Author)]

Because the method you open the file with is then also used to unpack the file.

[nice]

will be fixed?

So the problem is caused by total7zip, if I understand you correctly?

no.
by 7zip (both dll and standalone).