The widget does not have this feature on it. However, you can add it if you feel comfortable to edit the widget. This will create an option for subs only.
I recommend that you create a backup of the widget first before changing it.
JS tab - Line 41. Change from:
if ((userState.mod && userOptions['managePermissions'] === 'mods') || ((userState.vip || userState.mod) && (userOptions['managePermissions'] == 'vips')) || userState.broadcaster || (userOptions['otherUsers'].indexOf(user) !== -1)) {
To:
if ((userState.mod && userOptions['managePermissions'] === 'mods') || ((userState.vip || userState.mod) && (userOptions['managePermissions'] == 'vips')) || userState.broadcaster || (userOptions['otherUsers'].indexOf(user) !== -1) || (userState.sub && userOptions['managePermissions'] === 'subs')) {
FIELDS tab - From Line 66. Replace the "managePermissions" block from
"type": "dropdown",
"label": "Who can start video:",
"value": "mods",
"options": {
"streamer": "Streamer",
"mods": "Streamer + Mods",
"vips": "Streamer + Mods + Vips"
}```
To:
```"managePermissions": {
"type": "dropdown",
"label": "Who can start video:",
"value": "mods",
"options": {
"streamer": "Streamer",
"mods": "Streamer + Mods",
"vips": "Streamer + Mods + Vips",
"subs": "Subs only"
}```