[EDIT: short answer is to first do all the “SketchUp Fundamentals” courses at https://learn.sketchup.com …]
I know how to size objects accurately (type size after drawing), and move them accurately first by moving in red axis (then typing number) and green axis (typing a number). But the only way I know to have their location be exact is to draw them at the origin, then do two moves, and further should it touch any other object it combines with the other object and there’s no way to move it without corrupting the previous shapes.
As an example, let’s say we want a 20x10mm oval with two circular ends, centered at the origin.
So to make a 10x10mm rectangle with lower left corner at -5, -5, I draw it with lower-left corner at 0,0, type “10,10” to size accurately, then select it (space bar, lasso) , then go in move mode (M) drag it left a bit (mouse drag with right-arrow to constrain move to red axis), and type “5” to make the move 5mm. Then I repeat to move it down the green axis another 5mm, thus centering it on the origin. Surely there’s an easier way to do it?
Likewise I want a 10x10mm circle centered at 5,0. I draw a circle around the origin, diameter 5mm (click origin, drag a circle, type “5”). I then select it (space, lasso) and move it right 5mm (M, right-arrow+drag, type “5”). Then I move with copy, 10mm left, producing an infinity-type shape. But is there an easier way?
Now combine the two. I draw and position the rectangle first. Then I draw the first circle. Looks fine, but sketchup assumes they’re a fancy combined object and I can no longer move just the circle. So I draw the rectangle… then move it up the green axist a memorable amount (20, say), draw and position the circles, then move the rectangle back down 20. Again, easier way?? [EDIT: select one circle, right-click, and select “make group.” It will no longer attach to other drawing that touches it. If it makes sense for your object to have sub-groups, leave it as such. Alternatively, ungroup it once the fiddly editing is done.]
Then the final step: erasing the unneeded internal circular lines. Sometimes when I click them in select mode, it selects the whole curve I want to delete, basically intersection point to intersection point, and I hit delete. But other times it just selects a single facet (of the 24, say, sides I’m using to approximate a circle) and I have to select and delete many many times over and over. Easier way?