Hi @Anonymous ,
Do you want to Check in or Check out SP Library doc using PowerApps app only?
Currently, within PowerApps, there is no function supported to Check in or Check out SP Library doc. If you want to use PowerApps app to check in or check out SP Library doc, I afraid that there is no way to achieve your needs.
As an alternative solution, I think Customer connector could achieve your needs. You could consider create a custom connector based on Microsoft Graph REST API within your PowerApps, then within the custom connector, define the Check In and Check Out action based on the following action path:
Check In action path:
POST /drives/{driveId}/items/{itemId}/checkin
POST /groups/{groupId}/drive/items/{itemId}/checkin
POST /me/drive/items/{item-id}/checkin
POST /sites/{siteId}/drive/items/{itemId}/checkin
POST /users/{userId}/drive/items/{itemId}/checkin
Check Out action path:
POST /drives/{driveId}/items/{itemId}/checkout
POST /groups/{groupId}/drive/items/{itemId}/checkout
POST /me/drive/items/{item-id}/checkout
POST /sites/{siteId}/drive/items/{itemId}/checkout
POST /users/{userId}/drive/items/{itemId}/checkout
After that, you could create a connection to above custom connector in your app, then you could use the Check In and Check Out action within your app.
More details about creating a custom connector based on MS Graph REST API in PowerApps, please check the following blog:
https://gotoguy.blog/2017/12/17/access-microsoft-graph-api-using-custom-connector-in-powerapps-and-flows/
More details about creating custom connector in PowerApps, please check the following article or video:
https://www.youtube.com/watch?v=dBCS1nPsDiE
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/register-custom-api
Best regards,