If life gives you lemons, you make lemonade. If you don't have lemons, you plant the damn tree!
In this case, if a supplier doesn't have a solution all ready for you to import into your CRM Dynamics, then you implement the integration on your own using their API.

In most cases, they want you to validate your actions and in this article I'll try to explain how to do this when it requires Bearer Tokens.
This has been written with usage with CRM Dynamics in mind, but because this is Javascript, it can also be applied in any other web application.

For some reason Microsoft envisioned that nobody should be able to add multiple contacts to a lead and have those automatically moved to accounts and when a lead is qualified.
Mayby it works in their mind, but I know for a fact a lot of people do not work with leads as Microsoft has envisioned and desperately need a way to have multiple contacts and have these moved to accounts upon qualification.

The good news is, this can be done by creating a C# plugin.
The only bad news would be if you do not understand how writing and implementing plugins work and do not want to put time into learning this, then you're going to have a bad time.
If you want to manage CRM Dynamics and make use of all of the possibilities, I highly recommend you learn.
Otherwise I would recommend you find a partner to help you implement this or find click2deploy solution online.

When you need to access data that's in a different entity because it's in a lookup field for example, you could use Business Rules but to a certain extend. But what if you want or NEED to use javascript?
This is where the API for CRM Dynamics 365 comes in handy! You can write the code all by yourself using XMLHttprequest, but if you are like me not being a dedicated coder you tend to forget how to do it because you haven't done it in a long time.

Unfortunately populating lookup fields isn't that straight forward like the other fields with a simple set value.
If you thought about using something like
formcontext.getAttribute("field here").setValue("value here")
then you are not going to have a good time.