How about combining all parts of "The Beginning of the End" into a single campaign with the same name? I'm sure this question has already been asked, but maybe the author has changed their mind?

Yes, I've thought about it. But there's one problem - all my maps from this series are designed for 2+ hours of gameplay, in each of which the hero levels up to 33+ levels. It definitely doesn't make sense to transfer all the hero's skills, experience, etc. from one map to another, because after the first map of the campaign, the hero's level will be around 40. There are 2 possible solutions to the problem:

1) Limit the hero's development level. But this doesn't make sense on maps where the hero starts from scratch and reaches level 35.

2) The plot. The plot allows for a smooth transition. That is, after the "New Threat" map in "Path of the Outcast," the hero travels along the path of the outcast and loses most of his experience and skills. At the end of "Path of the Outcast," the hero passes through the gates of Hell, where he also loses all his skills and experience and starts the third part from scratch. At the end of the "In the Depths of Hell" map, the hero is transported through a portal near the Devil's Tower to the world of the living, where he could theoretically also lose all his skills and experience during the transfer. After the fourth part, in the fifth, the hero appears near the end, already leveled up, so there are no problems here. But with this arrangement:
a) What to do with the spells in the hero's spellbook? They can't just disappear.
b) What's the point of collecting maps into a campaign if most of them will still have to be started from scratch?
Otherwise, I would like to create a full-fledged campaign for the Tower, and I have already come up with a sequel campaign for Inferno, one of the maps of which is already ready.