I have discovered that if you can find the proper name of the modpack & put it into the search box at the top of the modpack list if you are lucky it will bring up a bit in the launcher with the option to install & if you click install it will add it back into the launcher. However, the name used for the file in the technic launcher files and the name required are not always the same thing- files called businessserver, for example, require you to put Dragontech into that search box. The launcher cannot recognise any modpacks you have not specifically added into this new launcher that way and the website only has the old copy & past links that are now useless. All deleting the data and starting a fresh like you suggest does is you cannot play any of your saved worlds, go on any of the servers you have ever been on using the modpacks. The past is simply deleted and you get a new bunch of modpacks. It does not unlock any new modpack adding options or any ability to recognise previous files if copy and pasted back in or anything else. In other words it doesn't solve my problem.
When I installed the new launcher I deleted the old launcher anyway. I couldn't simply update the old launcher.