A quick background on why these two Power BI service features is important.
Content can be shared with external guest users (B2B). External guest users (consumers) mostly have consumption experience. They either bring their own Power BI license or the home tenant (provider) assigns the license to them. Then, guest users can access the content (report, dashboard) with the URL. Also, if we want the guest users to build content on the shared dataset then they must be provided the dataset URL to build content, and the built content will be stored in the provider tenant.
Two things are tricky here! First, guest users can’t discover the shared artifacts in one place. Second, guest users with build permission on the shared dataset can’t create composite models on the shared dataset and save reports and dashboards in their own tenant.
Things are changing for the better!
Discoverability feature for B2B content
Guest users will now see a new tab “From external orgs” on their home page. This page lists all artifacts they have access to as a guest user.

The tenant that is sharing the dataset must turn on “Allow Azure Active Directory guest users to access Power BI” setting in Tenant settings to make this work.

In-place Dataset Sharing
Guest users can discover, connect, and work on the shared dataset in their own tenant. This also means they can create composite models by mixing shared dataset with other datasets and publish the composite model to service for reporting.
You may want to control which users/groups are allowed to share datasets across tenants, and whether authorized guest users can discover, connect, and work on the shared dataset in their own tenant. So, in tenant settings turn on “Allow specific users to turn on external data sharing” and “Allow guest users to work with shared dataset in their own tenants”

Then, share the dataset with the external user with “build” permission and turn ON “External sharing” on the dataset settings page.

Now, the guest user can discover and connect to the shared dataset in Power BI desktop. Guest users must use Power BI desktop September 2022 release or later and turn on “Connect to external dataset shared with me” in Preview features.
In Power BI desktop, the guest user can discover the external dataset in Data hub. Live connect mode is not currently supported for in-place dataset sharing. So, it changes the queries to DirectQuery mode building a composite model.

Guest users can either import/DirectQuery other available datasets to this composite model or publish this report to their Power BI service for building further reports.