
@Orlík Tomáš From the above comments' discussion, it seems that you want a SharePoint library to show in File Explorer, then could upload files from it into a web page. Is it right?
To achieve it, you can go to your SharePoint library and click "Sync" to put SharePoint files into a folder on your device that you can then manage with File Explorer.
More information about the settings, you can refer to the official article:
https://support.microsoft.com/en-us/office/map-a-network-drive-to-a-sharepoint-library-751148de-f579-42f9-bc8c-fcd80ccf0f53
------Update on 2022.4.28-----
MS Outlook can browse online content
Did you mean by the following?
Per my searching, this feature is just for Outlook currently. I searched online and internally, there is no similar plugin or roadmap for this requirement.
If you don't want to use OneDrive sync, as a workaround, you can consider viewing SharePoint files with File Explorer in Edge, you need to follow the steps in the article to configure your environment.
Besides, for this requirement, you can submit a user voice.
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