The phrase "are supposedly able to" is correct and usable in written English.
It can be used when discussing something that is claimed or believed to be possible, often with a sense of skepticism or doubt.
Example: "The new software update claims that users are supposedly able to access features that were previously unavailable."
Alternatives: "are said to be able to" or "are believed to be capable of".
The news discs are supposedly able to deliver higher sound quality than existing CDs.
Using a mic embedded in a remote, viewers are supposedly able to control certain functions with just their voice.
The come-on: Terabeam's laser transmitters, which are supposedly able to zap bits of laser light over the air at a terabit (one trillion bits a second).
The come-on: Terabeam's laser transmitters, which are supposedly able to zap bits of laser light over the air at a terabit, or one trillion bits per second.
By looking at the girls on video, viewers are supposedly able to reduce the level of nervousness the next time they encounter females in real life.
Buyers are supposedly able to recoup this cost within 16 years, 14 years faster than with existing condo-use fuel cell systems.
A brazen head, should you have forgotten your medieval history, is a brass head that was supposedly able to answer any question.
There is still a perception in the media that "if you're a young black guy then you're always talking about guns and gangs, and that's the only thing you're supposedly able to discuss".
As an adult I was supposedly able to make my own choices, but by then I had already galvanized myself against disappointment by expecting little, so that's what I got.
The agreements, however, proved to be of limited value, so pain specialists turned to diagnostic questionnaires that were supposedly able to predict whether a patient was likely to abuse a narcotic because of factors like a family history of substance abuse.
Japanese toymaker People [JP] recently released a bizarre invention that is supposedly able to turn all sleepyheads into early risers.
