I would run a script that outputs a CSV formatted list that you can copy/paste into a text document, save as myFile.csv, and then open that in Excel.
Example:
/ip dhcp-server lease
:foreach i in=[find] do={
:put ([get $i address].",".[get $i mac-address].",".[get $i client-id].",".[get $i server])
}
To get all the options, I do something like this. Copy/paste this into the terminal:
/ip dhcp-server lease
:foreach i in=[find] do={
:put ([get $i
Then, press TAB a few times until the list of options shows up:
/ip dhcp-server lease> :foreach i in=[find] do={
{... :put ([get $i
active-address agent-circuit-id comment lease-time status
active-client-id agent-remote-id disabled mac-address use-src-mac
active-mac-address always-broadcast dynamic radius value-name
active-server block-access expires-after rate-limit
address blocked host-name server
address-list client-id last-seen src-mac-address
...which you can then use to select which options you want to have in your CSV file. Just edit the first script to include the ones you want.