On our old TT with a manual awning, I used a clothesline tensioner with a 3/8 thru it and tied to the hooked to the ground anchors. It had a spring on it and required only a little pull to tighten and loosen it!
That said, I would not tie one down again, manual or electric!
One day at a park with the manual awning out and tied down and secured, an older seasoned camper that I know came by and made some valid points!
First, the rule is if its windy or raining, its best to stow it!
Second, he suggested that if it did get caught in a sudden burst of wind, that it would probably not hurt anything and you could put it in at that time, but you would know the conditions at the time!
Third, when you anchor the awning, you make it rigid and it couldn't move, Hence you are making a weak point for it to tear away like it wants to in a wind! If you are caught in a strong wind, maybe its best to let it go if you did not plan or ignored the existing winds! He point out that the weak point while anchored is probably going to be the mounts that your awning is attached to the RV with, Therefore you not only lose the awning, you have also damaged your gelcoat or whatever you have for the outer shell and stripped out mounting hole for the bolts or screws that holds it in place!
This is why I will never anchor an awning of mine again.
Also, when I went to get the de-flappers and things I needed to tie the awning down, I asked the dealer if it worked pretty well, He just smiled and told me that lots of people do it, but he personally does not and I didn't ask why he didn't, I just assumed it was his choice!
But he went on to tell me that he sells the things to anchor them but will not push them because there is no way he wants to be responsible for them failing to do what the RVer wants them to do!
I would do as was suggested, maybe use a tarp on your things, other wise I would stow the awning when I'm not around the RV!
The awnings were never intended to be anchored and that why they don't come with awnings!
Another point is that just last year, a camping neighbor called his insurance company to find out if the awning was covered on his new motor home?
The ins. Co. asked him if it had the wind and rain sensors, which it does. They pretty much told him that they would be more apt to cover the awning if the sensors failed but also suggested that if the awning, "sensors or not" was left out intentionally or they find evidence that there was sufficient time to put it away and it wasn't because you wanted to sit under it to stay dry during a rain, or to just catch a breeze and shielded from the sun they could reject a damage claim! He was however covered in the event of a mishap, but the best policy is to stow it if your not there !