They do automatically change to a fuscia color if you have under the view menu, Atomic Variables is checked. 

@zenterix Try disabling the plot anti-aliasing.  It may be a similar issue with font anti-aliasing where my laptop would slow to a crawl as it anti-aliased all the text in my display.  Maybe the same thing for plots?  At least it's worth a try.  I don't use Linux but I'm just offering a suggestion in hopes that it might help you. 

It may be some OpenJDK-Maple-OS issue with anti-aliasing.  It never occured until Maple 2021 when the switch was made.

You can make the standard interface resemble the classic interface.

Go to Tools -> options display tab
-- change input display to Maple notation
-- change output display to typeset notation
-- change Default format for new worksheets to Worksheet

Apply globally

Also when you save your files choose save as Classic worksheet (.mws)

This way Maple will act more like Maple's classic interface, not exactly but if you prefer that style you can at least mimic it. 

Maybe just simply abs(frac(-9.8))

@mmcdara 

Alternatively you could use the op command as a very rudimentary measure.

op(a)[1]
                   3

I'm sure it's just a typo but I think maybe you're missing a right side bracket.

((1+(y'(x))^2)^(-1)*1/y(x) ) = C

That aside it seems to work under maple 2020.  This is what I get ..

eq:= ((1+(y'(x))^2)^(-1)*1/y(x)) = C
                            
isolate(eq,y'(x))
                               
allvalues(%)
                                 

It works fine as you presented it. 

However the only way you get your answer is if Rc wasn't assigned a value.  If I change Rc:=Rc instead of Rc:=R2 as you wanted it then I get your "huh? what's that" answer.

Regarding copying everything into Mapleflow at once, I can't see at the moment but I will look into it.
***********edit update******* 
That seems to be a Mapleflow weakness, it's getting entered as a text container and can't be changed into an executable math container.  If I find a way I'll update this question but I'm stumped for now. 

Also this works.  Under Tools --> Options --> Display

Change Typesetting level from Extended to Maple Standard.  All your conversions in vector form can now be changed when you do the unit conversion.

add to your circle command to

circle(c,(x+4)^2+(y-3)^2=81,[x,y])

In Maple 2017 there is a debug icon.  If you click that, a new window should open with many options and you can click on quit.  You should end up back in Maple and can edit again. 

Maybe skip the ExcelTools Import and just use the plain Import - and import it as a Dataframe.

Is this what you mean?  int(f(x),x=a..b)  which is the same way to enter in Maple.  Or using the context menu on the left.

******edit added ***** additionally type int then press CTRL + spacebar  to bring up a list of options

You are using e as a variable Maple doesn't know you are trying to use it as a constant.

Change e^(-t) to exp(-t)

Press CTRL + R to add math in a text container.

Multiply value by Pi/180 to get radians.