The win probability is a fixed percentage for each stage. Our opportunities have varying probability at each stage so we would need be able to edit this manually each time. Is this possible?
I had this exact issue with HubSpot. Similar systems allow you to set an individual probablity from 0% to 100% for each individual deal.
The solution was to setup a custom field called 'Factor' that accepted integers. Of course this is not ideal as you need to train the sales team to only input a number from 0-100.
Then through the use of calculated fields, I was able to get all of the reporting I needed - for instance by multiplying the deal Amount by Factor, then dividing by 100 I can get the total factored value (or average weighted deal value).
We've built a Hubspot CRM add-on where you have individual probabilities for each deal instead of it being based on the stage, it's called Attentive.
Every time there's a new deal, Attentive will ping you via email (or Slack if you prefer) and ask you what's the win probability for that deal. If you don't reply to that, it'll default to the stage probability.
This means that you'll have a much more accurate probability-adjusted sales pipeline.
Hope this helps, let me know if I misunderstood your question,