Just started using it (switching from Milanote) and it looks very promising, but there are some things that are holding ti back I think.

Probably the top 2 things I use in Milanote that Thinker is lacking is boards and notes under images. Having canvases (or boards, whatever) within canvases (with icons) is the best way from comic artists like me to work imo. Also I need to put notes under images without it being a separate note. Technically I could just make a separate note and then group the note and image together, but that's just quite inconvenient when it should be a one-button sort of deal.

Also main critique is it's not very intuitive, like there are a lot of pretty icons, but I have no idea what any of the buttons do. I've been trying to create a writing document in my canvas for a while btu I simply cannot find the button. Make it so when you hover over an icon for a couple seconds, it says what the name of it is.

(Edit: In the Thinker preview there is a button to add a writing document, at the bottom all the way to the left, but it is not present Thinker Cloud.)

Other random notes...

On the side bar it says "S" "M" "L" "XL" which confused me heavily, until I realized it is the thickness of lines/shapes. Just make this a drag bar instead, and label it "Width" so it's easier for people to know the random T-shirt size lineup is actually regarding line thickness. Same situation with the other rows, I still don't know what the little square row is about. Like when making text, why the T-shirt sizes and not pixel size or drag bar? And if not wanting to make it pixel size, why not just call it "Title" "Subheading" "Body" etc?

While minimalism is good, Thinker takes it a bit too far regarding not labelling anything. I think it's very good for people who just want to have a visual board of things, but for intense and complicated projects that include both art, writing, and video, it isn't really a Milanote alternative at this point. To be fair, I think it's absolutely suitable for more simple projects or brainstorming.