"though challenging" is a correct and usable phrase in written English.
You can use this phrase to express an acknowledgment that something is difficult. For example, "The project is ambitious and though challenging, I am confident we can complete it successfully."
The wind instruments delivered the characteristic solos with panache, as though challenging their boss to engage even more energetically.
Though challenging for the layman, his book will reward persistent readers with a better understanding of the most controversial scientific issues of our day.
Instead of addressing the issue of a growing population of elders as a positive, though challenging, demographic change, he pits elders against kids.
Systemically approaching this issue both in the UAE and in the broader Gulf region to disrupt Taliban finances, while protecting commerce and economic activity, is an important, though challenging task.
Every so often he allows himself some lavish, graphic sexual writing, as though challenging us to read these descriptions any differently from his scenes of longing for lost family homes or missed landscapes.
Consider another scene from the same story: the foreign narrator has finally made it to the ear doctor — it wasn't easy, she gets delayed by "riddles" such as "A pair of ice skates and a clock lay side by side, as though challenging me to guess their relation.
The two images described above, though, challenge that reductive description.
The plots of the operas are similar: Young love, though challenged, wins in the end.
Guillaume, though challenged, is functioning at a high level in school.
Iraq, though challenged by the US over its allowance, has yet to interfere with Russian overflights.
Though challenged by Edwards over the next several months, Richards retained for nearly a year before losing to Kevin Steen.
