Funny, when I read the title I thought it was some mental trick that involved holding a pen.
The actual idea of 'holding pens' is a good one. However, only if the contents get sorted, otherwise they will just fill up with clutter. I know people for whom this idea would lead to excuse to not put things away, they'd just put them in the holding pen and do it later. Later never comes.
Same here. I came away wondering if I had fallen for click bait.
I try to stare hard at the thing I wish to put down for at least a count of two. That usually brings me "into the moment" and I put it where it belongs. I don't always remember to do it, but it works when I do.
The worst for me are my clip on sunglasses. I take them off when going inside and don't wish them in my pants pocket where they will get broken. Consequently, I tend to set them down "wherever" and lose track of them. Particularly when conditions change, e.g. dusk, when I go back out and they are no longer needed. Shirt pockets would resolve that issue, but I'm not going to change my my entire wardrobe to resolve this issue.
The actual idea of 'holding pens' is a good one. However, only if the contents get sorted, otherwise they will just fill up with clutter. I know people for whom this idea would lead to excuse to not put things away, they'd just put them in the holding pen and do it later. Later never comes.