It would be best to explain more broadly what you're trying to accomplish. Is the entire statement dynamically constructed from text, or are you simply trying to, for example, use indirect references to the widget names?

n1:"canvas_16"
n2:"canvas_1"
cw:images_color.widgets
c1:cw[n1]
c2:cw[n2]
c1.paste[c2.copy[]]

The eval[] function can be used to evaluate a dynamic snippet of Lil; it returns a dictionary with any syntax error information (if the snippet was malformed) or a result and variable bindings:

eval["2+3"]
# {"value":5,"vars":{}}

By default, eval[] is only aware of variable bindings (including definitions of built-in functions like eval[] itself, deck parts, etc) that you explicitly pass into it as a dictionary- its second optional argument. This makes eval[]-ed code "safe by default"; it is sandboxed to play only with what you give to it.

eval["a+b" ("ab" dict 11,22)]
# {"value":33,"vars":{"a":11,"b":22}}
z:99 eval["z+5"]
# {"value":5,"vars":{}}

If you do want to include local bindings, a truthy third argument will opt into including them; this means everything that was in scope from the caller's perspective will be available to the code snippet:

a:11
b:33
eval["a+b" () 1]
# {"value":44,"vars":{}}

As always, when exploring unfamiliar scripting functionality I recommend trying things step-by-step in the Listener.

Per your question, something like the following might work:

eval["canvas_16.paste[images_color.widgets.canvas_1.copy[]]" () 1].value

But, again, please take a step back and make sure this is what you really want to do. As problem-solving tools go, eval[] is something of a sledgehammer, and you may only need scissors or a pair of tweezers.

Make sense?