How to manually add vendor prefixes for flex to css-auto-prefix plugin (VS Code)?

Question

Visual Studio Code

I opened the defaultSettings.json file, found examples of prefixes there, but for display: flex; nothing is written there.
I decided to register in the user's Settings.json file. Added:
"css-auto-prefix.prefixes": {
"display": [
"webkit",
"moz",
"ms",
"o"
]
}
and it prefixes with the word display:
-webkit-display: flex; etc.
And it is necessary that they be added to flex:
display: -webkit-flex;
I put the word flex in the settings - nothing gives. In the plugin repository, the developers do not answer questions for at least a year.
Maybe someone will tellhow to properly configure it so that it is automatic and for display: flex; vendor prefixes were prescribed (I did not notice such problems in Sublime3).
P.S. I understand that this is the only more or less normal plug-in for VSK.