bootstrap studio image doesnt show in preview

You will not see the image in the app or previews since the images are not within BSS, but this way you can reference just like you did and as long as you put the images into that location directly (since they won't be within the Assets folder) they will show up just fine on export.

Use a relative location to an already uploaded location on the site (this would be my first choice if you're dealing with a lot of images as you can then manage them easier as well.). With a Custom Code block, there's no knowledge built into it, it's fully custom code so you need to tell it where exactly everything will be. The built in Links and Images sections are setup to read things as they will be when they are exported, so they already know where everything in the site is located. folders are all within an Assets folder so you cannot just reference them like within your code, because custom code blocks do not read the site like it an internal link/img does. Keep in mind that when the website exports, the CSS, Fonts, Img etc.

When you do custom code you need to do one of a few variations of the links to images, pages, etc.:

Bootstrap studio image doesnt show in preview