This area is for logo only. Price comparison is for Price comparison and
nothing else. Use other product layouts if you need coupons. Most of them
have good support of coupons.

I think there can be an area in this bar to show coupon info and other custom info, the customer will need to get some deals info instantly: https://prnt.sc/tqnx30

Maybe in your next update haha

Compare by sku is not fir coupon sites. But you can add coupon text inside short description of product. Or inside custom code areas 

http://rehubdocs.wpsoul.com/docs/rehub-theme/shop-options-woo-edd/extended-custom-product-areas/

But I need compare price by SKU, how can I do now, I don't need other layouts.

Use other product layout. You cant show coupons in content egg product
layouts.

http://rehubdocs.wpsoul.com/docs/rehub-theme/shop-options-woo-edd/product-layout/

Or add text to short description of product

I do set a coupon code: https://prnt.sc/tpxh5m

but the product doesn't show it, how can I show it in this bar? I really need it

https://prnt.sc/tpxgn6

You missed information how you set it

Please, follow this guideline and provide us all required information, screenshots what you did, links on pages, so we can check your problem and help you faster 

https://sizamtheme.support-hub.io/articles/how-to-write-to-support-if-you-need-technical-help

I do set a coupon code, but the product doesn't show it, how can I show it in this bar? I really need it