File concatenation

 awk '{$2=$2":"$8"-"$3;$3=$NF;$4=$NF="";print $0 | $10=$10":"$8"-"$18;$11=$NF;$12=$NF="";print $0 }'  design.txt 

Trying to concatenate specific fields in a spreadsheet and the others remain unchanged.

I attached an excel spreadsheet (all the data comes from a design.txt), but I put an example in there as well. Thank you :).

Insert a new column with a formula to concatenate the originals, them copy/paste values.

Not sure what you are after, If you have just 1 excel sheet, why not use an excel formula and delete the columns you don't need,

 
 =CONCATENATE(I2,":",J2,"-",K2)
 

If you want to use awk, just blank out the columns you don't want,

 
 awk '{$2=$2":"$8"-"$3;$6=$6":"$7"-"$8;$3=$4=$7=$8="";}1'  file
 

Not clear. Please be way more specific.

Do you want to work on a text file (with awk as in your sample code) or on a spread sheet (as indicated by post text and attachment)?

The awk script cannot run flawlessly. Do you want two lines (with different modifications) for every line in your input file? State in plain English what you want to have done.