As you know already, in one Table (Entity), we can create lots of Views. And by default, when we add that table in the form (as Lookup control), the User can see all the views and change it. That is why common in the business requirement to set the control to only use certain views (to minimize record selection) like in the below picture:

But when we are working in the Business Process Flow, we don’t have those options settable (below is a sample of my BPF):

When defining the lookup attribute, we only have those properties to set.
When interacting with the BPF here we can see the “Advance lookup” link:

After clicking that, the Advance dialog appeared > we can change the views (in our scenario, we don’t want the user to change the view in this control):

Solution
Whenever we create the BPF, the system will create a new table for us. When we try to open the Form definition of the BPF, unfortunately, we can’t change anything there:

But knowing this, I try to add this BPF (including the Table) into my solution and also a sample of the Lookup settings from the Form which I want to apply in the BPF later on:

Once you export the solution (must use unmanaged), I use below Microsoft Power Platform CLI command:
pac solution unpack -z .\Solutions\Blog_Customizations.zip -f .\Unpack\Blog_Customizations\ -e verbose
Once the unpack files are generated, you can try to check out the sample lookup that you already set:

I then copy those XML (the tag parameters) > open the BPF Entity\FormXml\main and add the properties XML inside it. So here are my changes before and after:

Once you did this, click save and then you need to pack the folder into the solution using the below command:
pac solution pack -z .\Solutions\Blog_Customizations_Fixed.zip -f .\Unpack\Blog_Customizations\
The last part is to import the Blog_Customizations_Fixed.zip and don’t forget to Publish All Customizations!
Here is the result:

Happy CRM-ing!