Open / Import opml-Files

I‘m using Omnioutliner 3.4 Pro with an iPad Pro / iOS 13 and want to Open / Import an opml-file

Today I tried this several times.

I have sent the opml file to me by mail and then tried to send it to omnioutliner.

I exported the file as an opml-file from mindnode and wanted to open the file in Omnioutliner.

I have not found a way to import or open the file.

Using my iPhone (Also with iOS 13) I‘m able to copy an opml-file using the „Open with“ command. On my iPad there isn‘t this option