+1 Yes, we need this feature. I'm old-school. I used to work with Macromedia Freehand, which already had this feature back in 2003... Yes, That's over 16 years ago. And the way it worked was brilliantly simple: All guides were automatically put on a special 'guides' layer. All you needed to do to convert an object to a guide was to move the object to the guides layer. Quick, simple, no hassle and a very useful feature. Personally I don't like Illustrator (the last version of Freehand - v11 - hasn't been updated since 2004 and is still better and faster than recent versions of illustrator. I purchased Affinity Designer 2 days ago, but the lack of this feature is a bit disappointing.