Computer-assisted solution
Here's my simple-minded Python code:
words = set(w.strip() for w in open('...')) # dictionary filename here
b1 = [['pricetag','gatekeeper']]
lengths = [8, 8, 8, 9, 8, 9, 8, 8, 9, 9, 10, 11, 8, 10, 8, 9, 9, 11]
def flat1(lists):
result = []
for l in lists: result.extend(l)
return result
for l in lengths:
candidates = flat1((prev+[w] for w in words if len(w)==l and w[:4] == prev[-1][:-5:-1]) for prev in candidates)
print(f'after length {l}, #candidates={len(candidates)}')
candidates = [c for c in candidates if c[-1].endswith('ator')]
It would be more efficient to work inward from both ends and then intersect in the middle, and/or to turn the list of words into a map from first 4 letters + length to corresponding words -- but computer time is cheap and simple code has fewer bugs.
(I have in fact implemented the second of those. It does make things way faster.)
I have three word-lists readily to hand on my computer, of different sizes. With the smaller two, or indeed with the union of the smaller two, no solutions were found. I assume they're missing some "ordinary" words. With the biggest, after maybe 10 minutes of grinding (I didn't actually time it so that might be way off) it finds 216 solutions. The one with the simplest words (measured by, first of all, how many are in my smallest wordlist, then by how many are in the second one) still has quite a number of obscurities in it:
pric//etag
gate/ke/eper
repe/ated
deta/iler
reli/eved
deve/l/oper
repo/rter
retr/i/ever
reve/rter
retr/aced
deca/l/iter
reti/c/uled
delu/st/ered
dere/gul/ated
deta/iled
deli/ne/ated
deta/iled
deli/g/hted
deth/r/oned
deno/min/ator
rota/v/irus
suri/na/mese
This one scores a little worse by my metric but seems maybe less obscure; only one word in it gives me pause:
pric//etag
gate/ke/eper
repe//ated
deta//iler
reli//eved
deve/l/oper
repo/rter
retr/e/ated
deta//iler
reli//eved
deve/l/oped
depo/s/itum
muti/ne/ered
dere/gul/ated
deta//iled
deli/ne/ated
deta//iled
deli/g/hted
deth/r/oned
deno/min/ator
rota/v/irus
suri/na/mese
All the solutions my computer finds contain at least one of the following words, the last of which I think isn't even a word:
reticuled, depositum, reticella, citicorp
I'm not very happy with any of these, so the next question is what words are missing from my list...
[EDITED to add:]
So, I looked at all the words in solutions found by my program, and reclassified some of them that were inexplicably-to-me omitted from the smaller word lists, and added to the large list everything that was in the smaller ones. The best solution found is still that last one, except that maybe
RETREATED/DETAILER is better than RETREATER/RETAILER.
The same list of inevitable obscurities applies to the solutions I found. I suspect there are still some holes in my lists.