yes the Restart Couatl does the trick but not the Reload Simbrief.
The Reload Simbrief works here, I suggested a Restart Couatl because you said it doesn't work for you.
first of all restarting couatl is a lottery and prone to crash and never start again.
This is something that never happens, instead, which seems to indicate something must be wrong with your install, which might explain also why the Reload Simbrief didn't work. I can restart Couatl here like 100 times in a row, it always restarts.
Are you sure it really crashed on Restart ? Try to be more accurate about this, because restarting is not a "lottery", and if it is on your system, it's worth investigating why.
and secondly I would like it to happen more seamlessly.
It is supposed to be seamless, but if you really are in a situation where you can't even Restart reliably, you have far bigger issues than just the Simbrief Reload not being seamless enough: the Couatl engine in MSFS has been designed to be restarted with no limitation, and it surely does it so, the real issue here is that it doesn't do that on your system.
Are you starting it as Admin ? If not, try to enable the "Start as Administrator" setting in the Compatibility settings of the Couatl64_MSFS.EXE file. If it's already enabled, try to disable it instead.
Same for the Windows 8 Compatibility setting: it's enabled by Default, before lots of users reported it fixed all their Restart problems, but a very few users reported the opposite, so you might need to check both cases and see the one that works best for you.